Process for producing molybdenum disulfide

ABSTRACT

A process for producing molybdenum disulfide from molybdenite ore sources is disclosed wherein the ore is digested in sulfuric acid under controlled conditions for a specific length of time. After digesting, the impure solid molybdenum disulfide is removed and admixed with hydrofluoric acid and hydrochloric acid under controlled conditions for a specific length of time. The solid molybdenum disulfide is then removed and washed.

I United States Patent [151 61,508

Ritsko 1 May 9, 1972 54] PROCESS FOR PRODUCING OTHER PUBLICATIONS MOLYBDENUM DISULFIDE Bunge, Chemical Abstracts, vol. 55, page 2037h I96] [72] Inventor: Joseph E. Ritsko, Towanda, Pa.

Primary Examiner-Oscar R. Vertiz 73 A 1 S l El t P od I I .sslgnee y vama ec nc r Assistant Examiner-Charles B. Rodman Flled: 14, 1970 Attarne \'Norman J. OMalley, Donald R. Castle and William 21 Appl. No.: 98,069 I McNem [57] ABSTRACT [52] U.S.Cl. ..23/l5 W, 23/19, 23/23,

23/134, 23/312 ME A process for producing molybdenum disulfide from molyb- [51] Int. Cl. ..C01g 39/00, C22b 49/00 denite ore sources is disclosed wherein the ore is digested in Field of Search 15 19 sulfuric acid under controlled conditions for a specific length ME of time. After digesting, the impure solid molybdenum disulfide is removed and admixed with hydrofluoric acid and [56] References cued hydrochloric acid under controlled conditions for a specific UNITED STATES PATENTS length of time. The solid molybdenum disulfide is then removed and washed. 1,895,811 1/1933 Morgan 8/l963 Tschudi et al. ..23/134 8 Claims, No Drawings PROCESS FOR PRODUCING MOLYBDENUM DISULFIDE BACKGROUND OF THE INVENTION 1 Field of the Invention This invention relates to molybdenum disulfide. More particularly, it relates to a process for producing molybdenum disulfide from molybdenite ore sources.

2. Prior Art Molybdenite ore generally contains molybdenum disulfide iron disulfide, calcium disulfide and lead disulfide in varying concentrations as its main constituents. Molybdenum disulfide usually accounts for about 40 percent to about 90 percent of the ore. The ore can be upgraded to about 98-99 percent molybdenum disulfide which is of sufficient quality to be used as a lubricant. The general method of upgrading the-ore is by flotation. Although the flotation can produce molybdenum disulfide of 98-99 percent purity, the yield is low, generally below about 70 percent. A second disadvantage can be the great expense of purchasing and setting up flotation equip ment.

It is believed, therefore, that a chemical process which produces molybdenum disulfide of 98-99 percent purity, suitable for use as a lubricant, in greater than 95 percent yields, even in ores containing as little as 40 percent molybdenum disulfide, is an advancement in the art.

SUMMARY OF THE INVENTION In accordance with one aspect of the invention, there is provided a process for producing molybdenum disulfide from molybdenite ore sources. The process comprises digesting molybdenite ore in sulfuric acid for at least about one hour at a temperature of at least about 240 C to form the first twophase system. The first two-phase system is diluted with'water at least twofold before separating the impure solid phase from the aqueous phase. The separated impure solid phase is admixed with a solution consisting essentially of from about 0.5N to about 3.5N hydrofluoric acid and from about 0.5N to about 2.5N hydrochloric acid for at least about 6 hours at a temperature of at least about 70 C to form the second twophase system comprising a partially purified solid molybdenum disulfide and an aqueous phase. The partially purified solid molybdenum disulfide is separated from the aqueous phase, and thereafter washed to form pure molybdenum disulfide.

DESCRIPTION OF THE PREFERRED EMBODIMENTS For a better understanding of the present invention, together with other and further objects, advantages, and capabilities thereof, reference is made to the following disclosure and appended claims in connection with the above description of one of the aspects of the invention.

The present invention relates to a process for producing molybdenum disulfide. Flotation has been the accepted procedure for producing molybdenum disulfide from molybdenite ores. Surprisingly, it has been found that molybdenum disulfide of a quality sufficient for use as a lubricant, can be produced from molybdenite ores by chemical methods.

Referring now to the invention with greater particularity, molybdenite ores can be digested in sulfuric acid for at least about 1 hour at a temperature of at least about 240" C to thereby form a first two-phase system comprising a solid impure molybdenum disulfide and an aqueous phase. The weight ratio of molybdenite ore to sulfuric acid is from about 1:1 to about 1:3, depending on the quality of the ore and the percent molybdenum present in the ore. Generally, the higher the molybdenum concentration, the less sulfuric acid is necessary. Although ratios greater than about 1:3 can be used, the aforementioned ratio is usually sufficient and the use of more sulfuric acid can cause handling problems and, of course, expense. It is critical that the molybdenite be digested at a temperature of at least 240 C, with about 260 C to about 280 C being especially preferred, to insure that essentially all iron pyrites present are dissolved. Below about 240 C dissolution is usually incomplete. Temperatures greater than about 300 C are generally=avoided for economic and safety reasons.

After digesting, the first two-phase system is generally allowed to cool to about C before diluting the system at least about twofold to reduce the acid concentration in the:

aqueous-phase. Coolingis not necessary, but it does reduce the amount of fuming and spattering when the two-phase.

system is diluted. The dilution can be accomplished by normal method of diluting acid, for example, slowly adding the twophase system to water. Generally from about twoto about 10- fold increase in volume is within the optimum range for handling purposes. Less than a two-fold dilution results in excessive heat and fume evaluation during subsequent processing. The solid impure molybdenum disulfide is then separated I from the aqueous phase by methods known to one skilled in the art, such as by filtering decanting, or centrifuging.

The solid impure molybdenum disulfide is then admixed with a solution consistingvessentially of from about-0.5N to 3.5N hydrofluoric acid and about 0.5N to about 2.5N hydrochloric acid for at least about 6 hours at a temperature of at least'about 70 C to form a second two-phase system comprising partiallypurified solid molybdenum disulfide and an aqueous phase. The weight ratio of the impure solid molybdenum disulfide to the prescribed acid solution is from about 4:1to about 1:1, depending on the amount of silica, and iron oxide present. Generally about 1.5N to about 3.5N hydrofluoric acid is sufficient to dissolve the silica present. The preferred normality will vary, depending on the amount of silica present. Likewise, about 0.5N to about 2.5N hydrochloric acid is sufficient to dissolve the lead present, with the preferred normality depending on the amount of lead present. The hydrochloric acid will also dissolve any iron present as Fe O Temperatures of from about 70 C to about 100 C will usually insure complete dissolution. Below about 70 C some lead and silica can remain as a solid. Temperatures of about 100 C are generally unnecessary and avoided for economic andsafety reasons. Maintaining the temperature at about 70 C to about 100 C for about 6 hours to about 24 hours has proven sufficient.

The partially purified solid molybdenum disulfide is separated" from the aqueous phase by methods known to one skilled in the art, such as filtering, decanting, or centrifuging. The molybdenum disulfide is then washed with water until a pH of about 6.5-7.5 in the wash water is obtained to insure complete removal of any entrained impurities and to yield essentially pure molybdenum disulfide. The final product can be used as a lubricant as is or milled to a finer size to suit the end use.

In order to more fully illustrate the preferred embodiments of the invention, the following detailed examples are given. All parts, proportions and percentages are by weight unless otherwise given.

EXAMPLE I About 250 pounds molybdenite ore, assaying about 66% M05 with the remainder being various impurities as shown in Table I, are slowly added to about 30 gallons of 3.6N sulfuric acid which has been heated to about 200 C. The mixture is heated to greater than 240 C, while agitating, for about 2 hours. The mixture is then cooled to below about C and dropped into about 200 gallons of cold water. After agitating and settling, the mother liquor is removed and the solid M08 is washed. A solution containing about 25 pounds HF and about 40 pounds HCI dissolved in about 100 gallons water is then added and the resultant mixture is digested for at least about 6 hours at a temperature of at least about 70 C. The mother liquor is removed and the solid M08 is washed with water until about neutral and then filtered. The resultant M08 is greater than 99 percent pure and of sufficient quality to be used as a lubricant, as is illustrated in Table 1.

TABLE l Element Ore Analyses MoS, after purification Mo 40% v 59.5% Fe 9% 0.05% Cu 5% 5 p.p.m. Si 5% 0.18% Pb 1% 0.005% A1 1% 0.05% Ca 1% 0.01% Ti 0.5% 25 p.p.m. Mg 0.1% 50 p.p.m. Zn 0.1% Bi 200 p.p.m. Ag 50 p.p.m. 5 p.p.m. Ba 50 p.p.m. Co 50 p.p.m. Mn 50 p.p.m. 1 p.p.m. Sr 50 p.p.m. V 50 p.p.m. 5 p.p.m. Cr 25 p.p.m. Ni 25 p.p.m. l p.p.m. B 6 p.p.m.

EXAMPLE II About 225 pounds of molybdenite ore, assaying about 58% M08 about 12% Fe, about 7% Cu, and the remainder being essentially the same impurities as shown in Table 1 are slowly added to about 30 gallons of 36N sulfuric acid, which has been heated to about 200 C. The mixture is heated to about 270 C, while agitating, for about 2 hours. The mixture is then cooled to about 150 C and added to about 200 gallons of cold water. After agitating and settling, the mother liquor is removed and the solid, M08 is washed. A solution containing about 20 pounds HF and about 40 pounds HCl dissolved in about 100 gallons water is then added and the resultant mixture is digested for at least about 6 hours at a temperature of at least about 70 C. The mother liquor is removed and the solid MoS is washed with water until about neutral and then filtered. The resultant M052 is greater than 99 percent pure and of sufficient quality to be used as a lubricant.

EXAMPLE Ill Essentially the same procedure as in Example II is used on about 200 pounds of molybdenite ore, assayed at about 40% M05 about 20% Fe, about 8% Cu, and the remainder being essentially the same impurities as. shown in Table l. The resultant M08 is greater than 99 percent pure and of sufficient quality to be used as a lubricant.

EXAMPLE IV Essentially the same procedure as in Example I is used on about 250 pounds of molybdenite ore, assayed at about 78% M08 about 5% Fe, about 2 percent copper, and the remainder being essentially the same impurities as shown in Table I with essentially the same results as obtained in the aforementioned examples.

While there has been shown and described what are at present considered to be the preferred embodiments of the invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the scope of the invention as defined by the appended claims.

1 claim:

1. A process for producing molybdenum disulfide from molybdenite ores which comprises:

a. digesting molybdenite ore in sulfuric acid in amounts sufficient to insure that essentially all iron pyrites present are dissolved, for at least about 1 hour at a temperature of at least about 240 C, to thereby form a first two-phase system comprising an impure solid molybdenum disulfide and an aqueous phase,

b. diluting said first two-phase system with water to achieve at least a twofold volume increase, c. separating said impure solid molybdenum disulfide from said aqueous hase, d. admixing sat impure sol d molybdenum disulfide with a solution consisting essentially of from about 0.5N to about 3.5N hydrofluoric acid and from about 0.5N to about 2.5N hydrochloric acid in a weight ratio of said molybdenum sulfide to said acid solution of from about 4:1 to about 1:1, for at least about 6 hours at a temperature of at least about C, to'thereby form a second twophase system comprising a partially purified solid molybdenum disulfide and an aqueous phase,

e. separating said partially purified solid molybdenum disulfide from said aqueous phase, and thereafter f. washing said partially purified solid molybdenum disulfide to form pure molybdenum disulfide.

2. A process according to claim 1, wherein the weight ratio of said molybdenite ore to sulfuric acid is from about 1:1 to about 1:3.

3. A process according to claim 1, wherein said digesting temperature is from about 240 C to about 300 C.

4. A process according to claim 3, wherein said digesting temperature is from about 260 C to about 280 C.

5. A process according to claim 1, wherein said digesting time is from about 1 hour to about 3 hours.

6. A process according to claim 1, wherein said first twophase system is diluted with water to achieve from about a twofold to about a tenfold increase in volume.

7. A process according to claim 1, wherein said temperature during said admixing step is from about 70 C to about C.

8. A process according to claim 1, wherein the time of said admixing step is from about 6 hours to about 24 hours. 

2. A process according to claim 1, wherein the weight ratio of said molybdenite ore to sulfuric acid is from about 1:1 to about 1:3.
 3. A process according to claim 1, wherein said digesting temperature is from about 240* C to about 300* C.
 4. A process according to claim 3, wherein said digesting temperature is from about 260* C to about 280* C.
 5. A process according to claim 1, wherein said digesting time is from about 1 hour to about 3 hours.
 6. A process according to claim 1, wherein said first two-phase system is diluted with water to achieve from about a twofold to about a tenfold increase in volume.
 7. A process according to claim 1, wherein said temperature during said admixing step is from about 70* C to about 100* C.
 8. A process according to claim 1, wherein the time of said admixing step is from about 6 hours to about 24 hours. 